The present invention relates generally to flow scales for sensing the flow of solid materials. More particularly, the present invention relates to a flow scale of a type using an impact plate for sensing the flow of materials directed against the impact plate.
In a variety of applications, it is frequently desirable to measure characteristics of a flow of solid materials, such as granular and powdered materials, without significantly interrupting the flow. Flow scale designs are known that incorporate an impact plate disposed substantially vertically, such as Tomiyasu et al., U.S. Pat. No. 3,640,135. The flow of solid materials is directed against the impact plate whereupon a horizontal force component exerted upon the impact plate is detected. When combined with weight data from another scale, information such as the flow rate and the weight of solid materials displaced can be determined.
Flow scales are often used under adverse environmental conditions. For example, flow scales are often used in environments with a high dust content, which hinders operation of mechanical and other sensitive components of the flow scale. Material buildup on or around mechanical components of the flow scale, such as at a mechanical support for the impact plate, may produce undesirable hysterisis effects that reduce sensitivity and accuracy of the flow scale.
Moreover, flow scales are also often used under unfavorable thermal conditions. As one example, hot baghouse dust may be present where flow scales are used in measuring paving mixes, and the heat from the hot baghouse dust may be transmitted (e.g., by conduction) to sensitive components of the flow scale. In addition, hot corrosive gasses may be present near the sensing device, due to material flow through the flow scale. Sensing devices like load cells are highly sensitive to high temperatures and corrosion, which can hinder or prevent proper functioning of the load cells and thus the flow scale.
Thus, the present invention relates to an impact flow scale that addresses problems with prior art designs.